Nanoporous laminates

ABSTRACT

A process of making a nanoporous substrate, such as the matrix in an electrical laminate, by grafting onto an organic resin backbone a thermolabile functionality by reacting hydrogen active groups of the organic resin with a compound containing thermolabile groups; then thermally degrading the thermolabile groups grafted on the organic resin to form a nanoporous laminate. Advantageously, the nanoporous electrical laminate has a low dielectric constant (Dk) because of the nanopores present in the laminate matrix.

FIELD OF THE INVENTION

The present invention relates to a process for preparing nanoporoussubstrates, such as electrical laminates having a low dielectricconstant.

BACKGROUND OF THE INVENTION

It is known to make electrical laminates and other composites from afibrous reinforcement and an organic matrix resin such as anepoxy-containing matrix. Examples of suitable processes usually containthe following steps:

(1) An epoxy-containing formulation is applied to, or impregnated into,a substrate by rolling, dipping, spraying, other known techniques and/orcombinations thereof. The substrate is typically a woven or nonwovenfiber mat containing, for instance, glass fibers or paper.

(2) The impregnated substrate is “B-staged” by heating at a temperaturesufficient to draw off solvent in the epoxy formulation and optionallyto partially cure the epoxy formulation, so that the impregnatedsubstrate can be handled easily. The “B-staging” step is usually carriedout at a temperature of from 90° C. to 210° C. and for a time of from 1minute to 15 minutes. The impregnated substrate that results fromB-staging is called a “prepreg.” The temperature is most commonly 100°C. for composites and 130° C. to 200° C. for electrical laminates.

(3) One or more sheets of prepreg are stacked or laid up in alternatinglayers with one or more sheets of a conductive material, such as copperfoil, if an electrical laminate is desired.

(4) The laid-up sheets are pressed at high temperature and pressure fora time sufficient to cure the resin and form a laminate. The temperatureof this lamination step is usually between 100° C. and 230° C., and ismost often between 165° C. and 190° C. The lamination step may also becarried out in two or more stages, such as a first stage between 100° C.and 150° C. and a second stage at between 165° C. and 190° C. Thepressure is usually between 50 N/cm² and 500 N/cm². The lamination stepis usually carried out for a time of from 1 minute to 200 minutes, andmost often for 45 minutes to 90 minutes. The lamination step mayoptionally be carried out at higher temperatures for shorter times (suchas in continuous lamination processes) or for longer times at lowertemperatures (such as in low energy press processes).

Optionally, the resulting laminate, for example, a copper-clad laminate,may be post-treated by heating for a time at high temperature andambient pressure. The temperature of post-treatment is usually between120° C. and 250° C. The post-treatment time usually is between 30minutes and 12 hours.

The current trend of the electrical laminates industry requiresmaterials with improved dielectric properties including lower dielectricconstant (Dk) and loss factor (Df); superior thermal propertiesincluding high glass transition temperature (Tg) and decompositiontemperature (Td); and good processability.

Heretofore, various methods have been used to try to improve thedielectric constant of electrical laminates made from epoxy-containingresin compositions including, for example, by adding variousthermoplastic additives, such as polyphenylene oxide (PPO),polyphenylene ether (PPE), or allylated polyphenylene ether (APPE), tothe epoxy-containing resin composition.

It is desired to provide a new pathway to reduce the dielectric constantof electrical laminates made from organic resins. More particularly, itis desired to prepare modified organic resins, such as epoxy-containingresins, with thermolabile groups to lead to nanoporous matrixes uponcuring.

SUMMARY OF THE INVENTION

The present invention is directed to a process of making a nanoporousmatrix in an electrical laminate by grafting onto an organic resinbackbone a thermolabile functionality by reacting the hydrogen activegroups of the organic resin with a compound containing a thermolabilegroup; and then thermally degrading the thermolabile groups grafted onthe organic resin, such that a nanoporous matrix is prepared. Suchnanopores provide a low dielectric constant because of the air presentin the nanopores and the lowest dielectric constant is for air.

In one embodiment, the present invention is directed to a process ofmaking nanoporous epoxy-based electrical laminates by modifying theepoxy resin backbone with a thermolabile group through the reaction ofthe hydroxyl groups of the epoxy resin, and then by thermally degradingthe thermolabile groups. Advantageously, the nanoporous electricallaminate has a low dielectric constant (Dk) because of the nanoporespresent in the matrix. The process of the present invention alsoprovides the following benefits: a nanoporous matrix with a controlleddispersion of nanopores; a controlled size of nanopores; a closeporosity; and a standard processability of the laminate.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Generally, the process of the present invention includes, as a firststep, reacting (a) an organic resin having hydrogen active groups with(b) a compound containing a thermolabile group, so as to graft thethermolabile group onto the backbone of the organic resin by thereaction of the compound containing the thermolabile groups with thehydrogen active groups of the organic resin.

In a second step, the thermolabile groups are degraded by subjecting themodified organic resin to a sufficient temperature, typicallytemperatures of from about 120° C. to about 220° C., to thermallydegrade the thermolabile groups, which in turn produces nano size voidsin the organic resin matrix. In laminate production, heating the organicresin for thermolabile group degradation is typically carried out duringthe pressing step of the laminate.

In one embodiment of the present invention, the organic resin may beselected from epoxy resins, phenolic resins, polimide resins, polyamideresins, polyester resins, polyether resins, bismaleimide triazineresins, cyanate ester resins, vinyl ester resins, hydrocarbon resins,and mixture thereof. The hydrogen active groups can be selected from,for instance, amines, phenols, thiols, hydroxyls or alcohols, amides,lactams, carbamates, pyrroles, mercaptans, imidazoles, and guanidine.

In another embodiment of the present invention, the compound containinga thermolabile group may be a dicarbonate and its derivatives, acarbazate and its derivatives, and other compounds containing tert-butylcarbonate. Examples of compounds containing thermolabile group are, butnot limited to, di-tert-butyl dicarbonate; di-tert-amyl dicarbonate,diallyl pyrocarbonate, diethyl pyrocarbonate, dimethyl dicarbonate,dibenzyl dicarbonate, tert-butyl carbazate and mixtures thereof. Thetert-butyl carbonate thermolabile group is advantageously stable to manynucleophiles and is not hydrolyzed under basic conditions, but it may beeasily cleaved under mid-acidic conditions or by thermolysis.

In one particular example of the present invention, epoxy resinscontaining hydroxyl groups or phenolic resins can be advantageously usedas the organic resin because epoxy resins are widely used in theelectrical laminates industry and epoxy resins offer goodprocessability. Di-tert-butyl dicarbonate can be conveniently used asthe thermolabile group-containing compound because it is commerciallyavailable in large volumes.

In the present invention, the initial unmodified epoxy resin used may beany known epoxy resin chosen for its expected performance, for example,brominated or bromine-free standard or high Tg standard, or low Dkstandard and the like. The thermolabile groups (also called “foamingagent”) are grafted on the epoxy backbone through the reaction with thehydroxyl groups. The modified resin is stable at ambient temperature.During polymerization, thermolabile groups degrade, leading to gasgeneration which, in turn, produce voids in the polymerized epoxy resinmatrix. Because the foaming agent is directly grafted onto the epoxymolecule, the statistical repartition of the voids is highly improved incomparison to the addition of non-grafted foaming agents. As aconsequence, the voids in the epoxy matrix are smaller (e.g., thediameter of the voids may be less than 200 nm) and well-dispersed withinthe laminate. The continuous epoxy matrix gives thermal resistance andmechanical integrity to the system, whereas the voids decrease thedielectric constant, resulting in low Dk electrical laminates. Forexample, generally, laminates having a Dk measured at 1 GHz of less than5 may be obtained, however, laminates having a Dk measured at 1 GHz ofless than 4.2, preferably less than 4.0, more preferably less than 3.8,even more preferably less than 3.5, may be obtained.

In one embodiment of the present invention, an epoxy resin is reacteddirectly, in an aprotic solvent, with a compound containing athermolabile group to form a modified epoxy resin.

In another embodiment of the present invention, the thermolabile groupis first reacted with a phenolic compound and then the resultingreaction product, a modified phenolic compound, is used as a curingagent to react with an epoxy resin, such as to introduce thethermolalide groups into the epoxy resin and form a modified epoxyresin.

The amount of thermolabile group used is selected such that the weightpercent of thermolabile groups in a final formulation or varnishcomposition is from about 0.01 weight percent (wt %) to about 10 wt %,preferably from about 0.1 wt % to about 5 wt %, and more preferably fromabout 0.2 wt % to about 2.5 wt %. The weight percentage of thecomposition above is given based on solids.

Optionally, a catalyst can be added to the composition to accelerate thereaction between the compound containing the thermolabile group and thehydrogen active groups of the organic resin. For example, hydroxylamineis known to catalyze the tertiary butoxy carbonylation of alkylamines atroom temperature (˜25° C.). In another example, dimethyl aminopyridyneacts as a catalyst for the reaction between hydroxyl groups or phenolsand di-tert-butyl dicarbonate at room temperature. Other catalystsuseful in the present invention include, for example, auxiliary basessuch as triethylamine or N,N-diisopropylethylamine.

To prepare a modified epoxy resin of the present invention, an epoxyresin having an average of more than one epoxy group per molecule and,on average, more than zero hydroxyl group per molecule may be used. Theepoxy resin may be selected from (1) an epoxy resin having an average ofmore than one epoxy groups per molecule and, on average, one or morehydroxyl groups per molecule, (2) a mixture of (1) and an epoxy resinhaving an average of more than one epoxy groups per molecule but nohydroxyl groups. The exact selection of the epoxy resin component isdetermined from the intended properties of the final products. Suitableepoxy resins, as used herein, include, for example, those having anepoxy equivalent weight of about 170 to about 3,500. Such epoxy resinsare well described in, for example, U.S. Pat. Nos. 4,251,594; 4,661,568;4,710,429; 4,713,137; and 4,868,059, and The Handbook of Epoxy Resins byH. Lee and K. Neville, published in 1967 by McGraw-Hill, New York, allof which are incorporated herein by reference.

Epoxy resins, which can be used as one epoxy resin component in thepresent invention, may be represented by the general Formula (I):

wherein A is independently a divalent chemical bond, a divalenthydrocarbon group suitably having from 1 to about 10, preferably from 1to about 5, more preferably from 1 to about 3 carbon atoms, —S—, —S—S—,—SO—, —SO₂—, —CO—or —O—; each R is independently a hydrogen atom or analkyl group suitably having from 1 to about 3 carbon atoms; each X isindependently a hydrogen atom or an alkyl group suitably having from 1to about 10, preferably from 1 to about 5, more preferably from 1 toabout 3 carbon atoms, or a halogenated atom such as Br or Cl; and n is anumber lower than about 12.

To further improve heat resistance, the epoxy resin component used inthe present invention may comprise a multi-functional epoxy resin havingan average of more than two epoxy groups per molecule. Preferredmulti-functional epoxy resins include, for example, cresol-formaldehydenovolac epoxy resin, phenol-formaldehyde novolac epoxy resin, bisphenolA novolac epoxy resin, dicyclopentadiene phenol Novolac epoxy resin,tris(glycidyloxyphenyl)methane, tetrakis(glycidyloxyphenyl)ethane,tetraglycidyldiaminodiphenylmethane and mixtures thereof. To prevent theresultant reaction product from having high viscosity,tris(glycidyloxyphenyl)methane, tetrakis(glycidyloxyphenyl)ethane andtetraglycidyldiaminodiphenylmethane are preferred. In view of costperformance, a cresol-formaldehyde novolac epoxy resin,phenol-formaldehyde novolac epoxy resin and bisphenol A novolac epoxyresin are preferred. In view of dielectric performance,dicyclopentadiene phenol novolac epoxy resin is preferred. In addition,it is preferable to use a multifunctional epoxy resin having narrowmolecular weight distribution (e.g., a Mw/Mn value of from about 1.5 toabout 3.0).

Optionally, a suitable organic solvent can be used during thepreparation of the modified organic resin of the present invention tolower the viscosity of the resin. Suitable organic solvents useful inthe present invention include solvents that do not contain hydrogenactive groups. Preferably, aprotic solvents may be conveniently used,such as, for example, ketones such as acetone, methyl ethyl ketone(MEK), and methyl isobutyl ketone; acetate of glycol ethers such aspropylene glycol monomethyl ether acetate (DOWANOL PMA); aromaticorganic solvents such as toluene and xylene; aliphatic hydrocarbons;cyclic ethers; halogenated hydrocarbons; and mixtures thereof.

In one specific embodiment for illustration purposes, thermolabilet-butyloxycarbonyl groups may be grafted onto an epoxy backbone throughthe reaction with hydroxyl groups. For example, brominated epoxy resinssuch as D.E.R. 560 or D.E.R. 539-EK80 and non-brominated epoxy resinssuch as D.E.R. 669E, all commercially available from The Dow ChemicalCompany, may be successfully modified in industrial solvents such as MEKor DOWANOL PMA.

In another specific embodiment, phenolic resins and phenolic derivativesmay also be modified according to the present invention. A few examplesof commercially available phenolic resin include cresol novolac;bisphenol A novolac such as BPN17, commercially available from Arakawa;and mixtures thereof. Examples of phenolic derivatives include bisphenolA, bisphenol F, bisphenol S, tetrabromo bisphenol A, hydroquinone, andmixtures thereof. Other phenolic resins and phenolic derivativesincluding dihydric phenols, halogenated dihydric phenols, polyhydricphenols, and halogenated polyhydric phenols useful in the presentinvention are described in PCT Application WO 01/42359A1 and TheHandbook of Epoxy Resins by H. Lee and K. Neville, published in 1967 byMcGraw-Hill, New York, all of which are incorporated herein byreference.

It is noteworthy that the organic resin shows generally a lowerviscosity in organic solvent after modification. Although not wishing tobe bound by any theory, it would appear that the lower solutionviscosity could be due to the decrease of the hydrogen-bonding effect,because of the grafting of the thermolabile group of the hydroxylfunctionalities.

In another specific embodiment for illustration purposes, epoxy resinsare partly or fully modified to epoxy carbonate resins, for example, bycarbonation of the epoxy group of an epoxy resin under CO₂ pressure atthe appropriate temperature, such as, for example, 80° C. with anadequate ion exchange resin. Such epoxy carbonate resins can be used asthe epoxy resin component to obtain modified epoxy resins withthermolabile groups.

The modified epoxy resins are advantageously used in producing alaminate. During the pressing stage of a laminate, for example, at 180°C., the thermolabile groups degrade and generate volatile products,creating a porous matrix within the laminate resulting in a laminatewith a reduced dielectric constant. Most of the key properties ofsystems using the present invention are not changed by the modifiedresins, such as varnish reactivity, prepreg processability, and laminateperformances, such as thermal properties, flame retardancy,drillability, chemical cleaning, and etching, and the like. However, thedielectric constant of the resulting laminate is advantageously reduced.Nanoporous laminates of the present invention may show an improvement ofup to 20% compared to the same epoxy system without nanopores. Becausethe foaming agent is directly grafted onto the epoxy molecule, voids aresmall (for example, 60 nm or less) and well-dispersed within thelaminate. For optimized processing conditions, the resulting laminate ishomogeneous and, depending on the formulation, may be transparent,opalescent or opaque.

Additional advantages for laminators using the modified epoxy resins ofthe present invention are that laminators can produce laminates withimproved dielectric constants, while at the same time, laminators cancarry on their expertise generated with previously existing epoxyproducts, i.e., same requirements for material handling, sameformulation techniques, and same production conditions. Moreover,laminators can use current glass reinforcements and copper foils. Theregistration of the laminates remains the same.

Additional advantages for producers of printed circuit boards, whichincorporate the modified epoxy resins of the present invention, are thatproducers can use production conditions that are similar to previouslyexisting epoxy systems. Producers can also obtain higher flexibility insystems design because they can tailor the dielectric constants of thesame base material depending on the level of porosity.

The epoxy resin compositions of the present invention may comprise, asan optional component, catalysts for catalyzing the reaction of theepoxy groups of the epoxy resin and the hydroxyl groups of the curingagent. Such catalysts are described in, for example, U.S. Pat. Nos.3,306,872; 3,341,580; 3,379,684; 3,477,990; 3,547,881; 3,637,590;3,843,605; 3,948,855; 3,956,237; 4,048,141; 4,093,650; 4,131,633;4,132,706; 4,171,420; 4,177,216; 4,302,574; 4,320,222; 4,358,578;4,366,295; and 4,389,520.

Examples of the suitable catalysts are imidazoles such as2-methylimidazole; 2-phenyl imidazole and 2-ethyl-4-methyl imidazole;tertiary amines such as triethylamine, tripropylamine and tributylamine;phosphonium salts such as ethyltriphenylphosphonium chloride,ethyltriphenylphosphonium bromide and ethyltriphenyl-phosphoniumacetate; and ammonium salts such as benzyltrimethylammonium chloride andbenzyltrimethylammonium hydroxide, and mixtures thereof. The amount ofthe catalysts used in the present invention generally ranges from about0.001 weight percent to about 2 weight percent, and preferably fromabout 0.01 to about 0.5 weight percent, based on the total weight of thereaction mixture.

In another specific embodiment for illustration purposes, imidazoles maybe partly or fully modified with a compound containing a thermolabilegroup to form a latent catalyst.

The epoxy resin composition of the present invention may comprise knowncuring agents. Such curing agents include, for example, amine-curingagents such as dicyandiamide, diaminodiphenylmethane anddiaminodiphenylsulfone; anhydrides such as hexahydroxyphthalic anhydrideand styrene-maleic anhydride coplymers; imidazoles; and phenolic curingagents such as phenol novolac resins; and mixtures thereof. Such curingagents can be added to the composition immediately before curing, or canbe included in the composition from the beginning if they are latent.The amount of the curing agents used may normally range from about 0.3to about 1.5 equivalent per epoxy equivalent of the epoxy components,and preferably from about 0.5 to about 1.1 equivalent per epoxyequivalent of the epoxy components.

Imidazoles can be used to promote epoxy homopolymerization. Depending onthe varnish composition, a pure homopolymerized epoxy network can beobtained, or a hybrid network can be formed between the homopolymerizedepoxy and the epoxy/hardener network.

The epoxy resin composition may also include a suitable organic solventcomponent to make handling of the epoxy resin varnish easier, and suchsolvents are added to lower the viscosity of the above compositions.Known organic solvents can be used. The solvents useful in the presentinvention include, for example, ketones such as acetone and methyl ethylketone; alcohols such as methanol and ethanol; glycol ethers such asethylene glycol methyl ether and propylene glycol monomethyl ether;acetate of glycol ethers such as propylene glycol monomethyl etheracetate; amides such as N,N-dimethylformamide; aromatic organic solventssuch as toluene and xylene; aliphatic hydrocarbons; cyclic ethers; andhalogenated hydrocarbons.

In the practice of the present invention, the amount of the organicsolvent employed may range from about 10 to about 60 parts by weight,and preferably from about 20 to about 40 parts by weight, based on 100parts by weight of the above epoxy resin composition.

To improve storage stability, the epoxy resin compositions of thepresent invention may comprise a suitable stabilizer. Suitablestabilizers, as used herein, include, for example, alkylphenylsulfonatesor halogenated alkylphenylsulfonates such as methyl-p-toluenesulfonate,ethyl-p-toluenesulfonate and methyl-p-chlorobenzenesulfonate. Apreferred suitable stabilizer used in the present invention ismethyl-p-toluenesulfonate. The stabilizer may suitably be used in anamount of from about 0.001 to about 10 weight percent, and more suitablyfrom about 0.01 to about 2 weight percent, based on the total amount ofthe composition.

As desired, the epoxy resin compositions of the present invention maycomprise an effective amount of other commonly employed additives forepoxy resins, for example, a reaction accelerator, pigment, dye, filler,surfactant, viscosity controller, flow modifier, flame retardant andmixtures thereof.

A process for preparing an electrical laminate using an organic resincomposition of the present invention will be described below.

In a first step, the organic resin composition of the present inventionis prepared by contacting an appropriate amount of the organic resinwith the compound containing the thermolabile group, and with optionaladditives, such as solvent and catalyst; and reacting the mixture tomodify the organic resin to introduce the thermolabile groups into theback bone of the organic resin resulting in a modified organic resin.

The reaction conditions for the above reaction are selected to insure anefficient reaction between the compound containing the thermolabilegroup and the hydrogen active group of the organic resin. The reactiontemperature is usually limited by the thermal stability of thethermolabile compound. The reaction generally processes around roomtemperature (about 25° C.), but can be from about 10° C. to about 50°C., preferably between about 15° C. and about 40° C., and morepreferably between about 20° C. and about 35° C.; for a period of fromabout 0.1 hour (h) to about 72 h, preferably from about 0.2 h to about24 h, and more preferably from about 0.5 h to about 12 h.

In a subsequent step, the above-modified organic resin, a curing agentand other desired additives are mixed to prepare a varnish. The varnishis then impregnated into a substrate or web. The obtained impregnatedsubstrate is dried at, for example, from about 90° C. to about 210° C.,and preferably about 130° C. to about 200° C.; for about 0.5 minute toabout 60 minutes, and preferably from about 0.5 minute to about 30minutes to obtain an organic resin-based prepreg. As used herein, thesubstrate may include, for example, glass cloth, glass fiber, glasspaper, paper, and similar organic substrates such as polyethylene,polypropylene, aramid fibers and polytetrafluoroethylene (PTFE) fibers.

In one specific embodiment of the present invention, the impregnatedsubstrate is dried below the decomposition temperature of the graftedthermolabile group. Consequently, no foaming or very limited foamingoccurs during the drying stage, resulting in a prepreg with an improvedcosmetic aspect.

The obtained prepreg is then cut into a desired size. One single cutprepreg or a plurality of cut prepregs (desired number, e.g., 2 to 10pieces) are laminated and subjected to pressing at a pressure of, forexample, from about 1 kgf/cm² to about 50 kgf/cm², and preferably fromabout 2 kgf/cm² to about 40 kgf/cm²; at a temperature of, for example,from about 120° C. to about 220° C.; for a period of time of, forexample, from about 0.5 hour to about 3 hours to obtain a laminate.During this heating step the thermolabile groups are degraded andnanopores are formed in the laminate.

In one embodiment, multi-stage pressing can be advantageously usedduring lamination. As an illustration, a lower pressure of, for example,from about 1 kgf/cm² to about 10 kgf/cm², may be first applied at alower temperature of, for example, from about 120° C. to about 160° C.,for a period of, for example, from about 0.1 h to about 1 h. Then, fullpressure of, for example, from about 5 kgf/cm² to about 50 kgf/cm², maybe applied at a higher temperature of, for example, from about 160° C.to about 220° C., for a period of time of, for example, from about 0.5 hto about 2 h. Multi-stage pressing can be used to control the morphologyof the nanoporous laminate. It has been generally observed that, for agiven volume fraction of voids, smaller and better dispersed pores leadto lower Dk than bigger and more aggregated pores.

An electrical conductive layer may be formed on the laminate with anelectrical conductive material. As used herein, suitable electricalconductive materials include, for example, electrical conductive metalssuch as copper, gold, silver, platinum and aluminum.

In another specific embodiment of the present invention, metal foil,such as copper foil, may be coated by the organic resin varnish of thepresent invention. The varnish then may be partly cured (B-stage) orfully cured (C-stage) to obtain a resin coated metal foil, such as resincoated copper foil.

The electrical laminates manufactured, as described above, can bepreferably used as copper clad laminates and multi-layer printed circuitboards for electrical or electronics equipment.

The present invention will be described in more detail with reference tothe following Examples and Comparative Examples, which are not to beconstrued as limiting. Unless otherwise indicated, “part” means “part byweight”.

The raw materials used for the chemical modifications and for thevarnish formulations in the Examples which follow were as follows:

D.E.R. 560 is a brominated epoxy resin, with an epoxy equivalent weight(EEW) of 450, commercially available from The Dow Chemical Company.

MEK stands for methyl ethyl ketone.

D.E.R. 539-EK80 is a brominated epoxy resin (80% nonvolatile (N.V.) inMEK), with an EEW of 450, commercially available from The Dow ChemicalCompany.

DIBOC stands for di-tert-butyl dicarbonate, and is commerciallyavailable from Aldrich.

DMAP stands for dimethyl amino pyridine, and is commercially availablefrom Aldrich.

DOWANOL PM is a propylene glycol monomethyl ether, commerciallyavailable from The Dow Chemical Company.

DOWANOL PMA is a propylene glycol monomethyl ether acetate, commerciallyavailable from The Dow Chemical Company.

DMF stands for dimethylformamide.

MeOH stands for methanol.

DICY stands for dicyandiamide (10% N.V. in DOWANOL PM/DMF 50/50).

2-MI stands for 2-methylimidazole (20% N.V. in MeOH).

2E-4MI stands for 2-ethyl-4-methylimidazole (20% N.V. in MEK or MeOH).

2-PhI stands for 2-phenylimidazole (20% N.V. in MeOH).

Boric acid (H₃BO₃) is used as 20% N.V. in MeOH.

Perstorp 85.36,28 is a phenol novolac (n=4.5—5) (50% N.V. in DOWANOLPMA), with a hydroxyl equivalent weight (HEW) of 104, commerciallyavailable from Perstorp.

D.E.N. 438 is an epoxy novolac (n=3.6) (80% N.V. in MEK), with an EEW of180, commercially available from The Dow Chemical Company.

EPPN502H is an epoxy novolac (80% N.V. in MEK), with an EEW of 170,commercially available from Nippon Kayaku.

MDI stands for 4,4′-methylenebis(phenyl isocyanate).

XZ 92505 is an epoxy/MDI flow modifier (50% N.V. in DMF), with an EEW of850, commercially available from The Dow Chemical Company.

XZ 92528 is a bromine-free epoxy resin (75% N.V. in MEK/DOWANOL PM),with an EEW of 325, commercially available from The Dow ChemicalCompany.

SMA 3000 is a styrene-maleic anhydride copolymer solution (50% N.V. inDOWANOL PMA/MEK), with an anhydride equivalent weight (AnhEW) of 393,commercially available from Atofina.

RICON 130MA13 is a maleinized polybutadiene, with an average molecularweight (Mn) of 2900, and an AnhEW of 762, commercially available fromSartomer.

SBM 1A17 is a styrene-butadiene-methyl methacrylate triblock polymer,commercially available from Atofina.

E.R.L. 4299 is a cycloaliphatic epoxy resin, with an EEW of 195,commercially available from The Dow Chemical Company.

BPN17 is a bisphenol A phenol novolac, with a phenol equivalent weightof 120, commercially available from Arakawa Chemicals.

E-BPAPN is an epoxydized bisphenol-A phenol novolac, 79.6% solids inacetone with an EEW of 197 (based on solids), commercially availablefrom The Dow Chemical Company.

TBBA stands for tetrabromo bisphenol-A.

D.E.R. 330 is a diglycidyl ether of bisphenol-A, with an EEW of 180,commercially available from The Dow Chemical Company.

D.E.R. 6615 is a solid epoxy resin, with an EEW of 550, commerciallyavailable from The Dow Chemical Company.

XZ-92535 is a phenol novolac solution, 50% solids in DOWANOL PMA, with ahydroxyl equivalent weight (OHEW) of 104, commercially available fromThe Dow Chemical Company.

D.E.R. 592-A80 is a brominated epoxy resin solution, 80% solids inacetone, with an EEW of 360 (based on solids), commercially availablefrom The Dow Chemical Company.

D.E.R. 669E is a high molecular weight diglycidyl ether of bisphenol-A,with an EEW of 3245, commercially available from The Dow ChemicalCompany.

XZ-92567.01 is a brominated epoxy resin solution, EEW of 385,commercially available from The Dow Chemical Company.

XZ-92568.01 is an anhydride hardener solution, with an EW of 398,commercially available from The Dow Chemical Company.

DMTA stands for dynamic mechanical thermal analysis.

The anhydride hardener solution (“AH 1”) used in the examples wasprepared as follows:

An anhydride hardener solution (AH 1) was prepared in a 10 L stainlesssteel reactor, equipped with a mechanical stirrer, and a heating jacket;and fitted with a N₂ inlet and a dropping funnel. 3671.9 Grams ofDOWANOL PMA and 3623.2 grams of solid SMA 3000 were charged into thereactor and the mixture was heated to 90° C. After complete dilution,730.7 grams of RICON 130MA13 was incorporated into the resultingsolution. The resulting solution turned white turbid. After 30 minutes,the resulting solution was allowed to cool down to 80° C. and 974.2grams of an SBM 1A17 solution in MEK (15% non-volatile) was introducedinto the solution in the reactor at 80° C. After complete cooling atambient temperature, the resulting anhydride hardener solution wasturbid whitish homogeneous. The theoretical anhydride equivalent weightwas 439 (based on solids).

The properties of the resultant laminates were tested using thefollowing testing methods and apparatuses:

(a) Dielectric Measurements

A Hewlett Packard Analyzer was used to measure Dk and Df in air, atambient temperature, from 1 MHz to 1 GHz. Sample size was about 10 cm×10cm with a thickness of about 1.5 mm.

(b) Nuclear Magnetic Resonance (NMR) Measurements

A Brucker apparatus operating at 250 MHz was used to determine ¹H— and¹³C-NMR spectra.

(c) Thermogravimetry Analysis (TGA)

A DuPont apparatus TGA V5.1A was used to determine the weight loss ofmodified epoxy resins from ambient temperature to 300° C.

(d) Optical Microscopy

100 μm thin sections were prepared with a rotating diamond saw. Thesections were studied with a LEICA POLYVAR 2 light microscope operatingwith transmitted light and differential interference contrast accordingNomarski. Images were captured with a Polaroid DMC digital camera.

(e) Transmission Electron Microscopy (TEM)

A glass fiber free epoxy area was sectioned perpendicular to the glassbundles with a LEICA ULTRACUT E ultramicrotome using a 45 degreesdiamond knife. The section thickness was 120 nm (setting). Sections werestudied with a CM12 transmission electron microscope operating at 120kV. Sections were collected onto cleaned, 300 mesh copper grids. Imagingwas recorded digitally in a Hitachi H-600 TEM at 100 kV. TEM micrographswere made of representative areas of the sections.

The standard methods used in the Examples to measure certain propertiesare as follows:

IPC Test Method Propery Measured IPC-TM-650-2.3.10B Flammability oflaminate [UL94] IPC-TM-650-2.3.16.1C Resin content of prepeg, by treatedweight [resin content] IPC-TM-650-2.3.17D Resin flow percent of prepreg[resin flow] IPC-TM-650-2.3.18A Gel time, prepreg materials [prepreg geltime] IPC-TM-650-2.3.40 Thermal stability [Td] IPC-TM-650-2.4.8C Peelstrength of metallic clad laminates [copper peel strength]IPC-TM-650-2.4.24C Glass transition temperature and z-axis Thermalexpansion by Thermal Mechanical Analysis (TMA) [Coefficient of ThermalExpansion (CTE)] IPC-TM-650-2.4.24.1 Time to delamination (TMA Method)[T260, T288, T300] IPC-TM-650-2.4.25C Glass transition temperature andcure factor by DSC [Tg] IPC-TM-650-2.5.5.9 Permittivity and losstangent, parallel plate, 1 MHz to 1.5 GHz [Dk/Df measurements]IPC-TM-650-2.6.8.1 Thermal stress, laminate [solder float test]IPC-TM-650-2.6.16 Pressure vessel method for glass epoxy laminateintegrity [high pressure cooker test (HPCT)]

EXAMPLE 1

A brominated epoxy resin, D.E.R. 560, was chemically modified withdi-tert-butyl dicarbonate groups using the following composition:

Component Amount D.E.R. 560  250 g DIBOC 30.4 g DMAP 1.01 gdichloromethane  200 g

A. Procedure of the Chemical Modification

The epoxy resin was first dissolved in dichloromethane (CH₂Cl₂) at 25°C. in an Erlenmeyer flask with a magnetic stirrer. After completedilution, solid di-ter-butyl dicarbonate was added to the resultingsolution. Then a solution of dimethyl amino pyridine in dichloromethanewas slowly charged into the solution in the flask. The resultingsolution was stirred at ambient temperature for about 18 hours to ensurecomplete conversion.

The dichloromethane was evaporated in a ROTAVAPOR under vacuum, fromambient temperature to 50° C. The dry resin was solid at roomtemperature.

B. Nuclear Magnetic Resonance (NMR) Characterization of the ModifiedBrominated Epoxy Resin

The ¹H—NMR and ¹³C—NMR spectra confirmed that chemical modification ofthe brominated epoxy resin and the grafting of the di-tert-butyldicarbonate groups onto the resin had occurred.

¹H-NMR

-   -   disappearance of —OH at 3.02 ppm        ¹³C-NMR    -   disappearance of carbon        at 69.6 ppm and shift toward carbon    -   appearance of methyl groups from tertio-butyl        at 27.84 ppm    -   appearance of quaternary carbon        at 82.44 ppm    -   appearance of carbonyl        at 152.79 ppm

These peaks are not due to free di-ter-butyl dicarbonate because thecarbonyl would appear at 146.5 ppm instead of 152.8 ppm.

C. Thermal Characterization of the Modified Brominated Epoxy Resin

The thermal characterization was done by TGA.

Before modification, D.E.R. 560 was stable to >200° C. D.E.R. 560started to decompose around 230° C.-250° C. because of the standardthermolysis of the bromine groups.

Modified D.E.R. 560 started to decompose at lower temperature because ofthe thermolabile groups. A significant weight loss was seen between 170°C. and 220° C. (4.77%), before the degradation of the bromine groups.The weight loss was due to the thermal breakdown of the thermolabilecarbonate groups grafted onto the resin backbone, leading to CO₂ andisobutene evaporation. At higher temperature (T>230° C.-250° C.), thestandard thermolysis of the bromine groups finally occurred.

Three other TGA runs were performed with different isotherm profiles.The resin weight loss was measured at the end of the isotherm:

-   -   (1) At the end of the isotherm at 180° C. for 4 minutes, the        weight loss was 0.72%;    -   (2) At the end of the isotherm at 185° C. for 60 minutes, the        weight loss was 4.48%; and    -   (3) At the end of the isotherm at 160° C. for 60 minutes, the        weight loss was 1.14%.

EXAMPLES 2A-2D

A brominated epoxy resin, D.E.R. 560, was modified with di-tert-butyldicarbonate groups using the same chemical modification procedure usedin Example 1, except with the compositions as show in Table I below.

TABLE 1 Example Example Example Example Component 2A 2B 2C 2D D.E.R. 560(g) 250 250 250 250 MEK (g) 118 118 118 DOWANOL PMA (g) 118 DIBOC (g)30.4 30.4 30.4 30.4 DMAP (g) 0.51 0.17 0.085 0.085

The modified resins in MEK or DOWANOL PMA could be used directly aftermodification, without stripping the reaction solvent.

TGA and NMR results on dried samples confirmed the modification of theepoxy resins.

EXAMPLE 3

A brominated epoxy resin, D.E.R. 560, was chemically modified withdi-tert-butyl dicarbonate groups using the same chemical modificationprocedure as the one described in Example 1, except using the followingcomposition:

Component Amount D.E.R. 560 2452.4 g DIBOC  147.2 g DMAP  0.41 g DOWANOLPMA 1400.1 g

Di-tert-butyl dicarbonate was charged to a reactor at ambienttemperature within 3 hours, and then the solution was kept at ambienttemperature for 4 hours.

The modified resin was used without further purification, and withoutstripping the DOWANOL PMA from the resin.

EXAMPLES 4A AND 4B

A brominated epoxy resin, D.E.R. 539-EK80, was partially modified withdi-tert-butyl dicarbonate groups using the composition as shown in TableII below.

TABLE II Component Example - 4A Example - 4B D.E.R. 539-EK80 (g) 617 416MEK (g) 54 24 DIBOC (g) 96 133 DMAP (g) 0.285 0.372 PROPERTIES weightloss between 6.6 14.1 170° C. and 220° C., measured by TGA (%)

The NMR spectra showed that the chemical modification was successful andthat no residual di-tert-butyl dicarbonate remained in the solution. NMRspectra also showed a portion of unreacted secondary hydroxyl groupsbecause of the under-stochiometric amount of di-tert-butyl dicarbonate.

EXAMPLE 5

In this Example, bisphenol A, a phenolic compound, was chemicallymodified with di-tert-butyl dicarbonate groups according to theprocedure described in Example 1. The composition used was as follows:

Component Amount bisphenol-A 114 g DIBOC 109 g DMAP 3.66 g dichloromethane 200 g

NMR, DSC and TGA characterization confirmed that bisphenol-A wasregenerated after heating to 220° C. and that degradation of thecarbonate groups occurred.

EXAMPLE 6

In this Example, a multifunctional phenol novolac resin, Perstorp85.36,28, was chemically modified in MEK with di-tert-butyl dicarbonategroups, using the procedure described in Example 1. Di-tert-butyldicarbonate was charged with an under-stochiometric ratio, therefore,only part of the phenolic groups were modified. The composition was asfollows:

Component Amount Perstorp 85.36,28 2.03 g DIBOC 0.24 g DMAP 0.67 mg MEK2.9 g

The successful modification was confirmed by NMR measurement. Afterheating to 220° C. and degradation of the carbonate groups, phenolic —OHgroups are regenerated.

COMPARATIVE EXAMPLES I AND II

In these Comparative Examples, azodicarbonamide, a known foaming agent,was used as an additive foaming agent and not grafted onto the organicresin; and compared with a reference material without azodicarbonamideor any other foaming agent as described in Table III below.

The incorporation of azodicarbonamide as a foaming agent into a resinleads to a non-stable varnish (precipitation overnight) and anon-homogeneous laminate (macrobubbles which leads to delamination).

TABLE III Comparative Example I Comparative Example II FORMULATION(reference) (with azodicarbonamide) XZ 92528 31.9 31.9 [75% N.V. inMEK/DOWANOL PM] (g) azodicarbonamide (g) 0.35 DICY 4.76 4.76 [10% inDMF/DOWANOL PM] (g) 2-PhI 1.18 1.18 [20% N.V. in MeOH] (g) PROPERTIESstroke cure reactivity @ 170° C. (s) 241 224 film Tg (° C.) 131 131varnish appearance clear yellow solution opaque orange dispersion,precipitation overnight pressing conditions 90 minutes @ 185° C., 90minutes @ 185° C., 125 N/cm² 125 N/cm² LAMINATE PROPERTIES laminateresin content (%) 42 41 laminate appearance yellow transparent whitishopaque, inhomogeneous, large bubbles between layers, delamination

EXAMPLES 7A AND 7B

In these Examples, a modified brominated epoxy resin, modified D.E.R.560, was used to prepare electrical laminate formulations, as describedin the following Table IV.

TABLE IV Example 7A Example 7B FORMULATION (50% modified D.E.R. 560)(100% modified D.E.R. 560) D.E.N. 438 31.53 36.03 [80% N.V. in MEK] (g)D.E.R. 560 17.29 [70% N.V. in cyclohexanone] (g) modified D.E.R. 56017.29 39.53 [70% in cyclohexanone] (g) Perstorp 85.36,28 40.34 46.10[50% N.V. in DOWANOL PMA] (g) DOWANOL PMA (g) 2.67 3.06 boric acidsolution 1.22 1.39 [20% in MeOH] (g) 2E-4MI 0.77 0.88 [20% N.V. in MeOH](g) PROPERTIES stroke cure reactivity @ 170° C. (s) 231 248 film Tg (°C.) 184 183 PREPREG PROPERTIES prepreg resin content (%) 45 47 prepregresidual gel time (s) 98 65 pressing conditions 90 minutes @ 185° C. 90minutes @ 185° C. 40 N/cm² 40 N/cm² LAMINATE PROPERTIES laminate colorwhitish translucent white opaque laminate Tg (° C.) 178 182

The above results show that the modified D.E.R. 560, prepared accordingto Example 1, did not change the reactivity of the resin and Tg remainedsimilar. Also, no thermal degradation was observed during a DSC scan ofthe fully cured laminate sample up to 230° C., which means that allthermolabile groups were degraded during the pressing stage. Byincreasing the amount of modified D.E.R. 560, the appearance of thelaminate changed from whitish translucent to white opaque because ofbigger and more numerous pores.

EXAMPLES 8A AND 8B AND COMPARATIVE EXAMPLE III

In these Examples, various amounts of modified D.E.R. 560, preparedaccording to Example 1, were used in resin formulations, as described inTable V below.

TABLE V Comparative Example III Example 8A Example 8B FORMULATION (0%modified D.E.R. 560) (50% modified D.E.R. 560) (100% modified D.E.R.560) D.E.N. 438 234.7 122.5 180.1 [80% N.V. in MEK] (g) D.E.R. 560 256.371.2 [70% N.V. in cyclohexanone] (g) modified D.E.R. 560 71.2 197.6 [70%in cyclohexanone] (g) Perstorp 85.36,28 299.9 165.3 230.5 [50% N.V. inDOWANOL PMA] (g) XZ 92505 56.1 [50% N.V. in cyclohexanone] (g) DOWANOLPMA (g) 15.0 boric acid solution 9.05 4.91 6.96 [20% in MeOH] (g) 2E-4MI5.17 3.36 4.77 [20% N.V. in MeOH] (g) PROPERTIES stroke cure reactivity@ 170° C. (s) 234 215 235 prepreg aspect shiny shiny slightly foamypressing conditions 90 minutes @ 190° C. 90 minutes @ 190° C. 90 minutes@ 190° C. 40 N/cm² 48 N/cm² 7 N/cm² LAMINATE PROPERTIES color yellowpale yellow white opaque translucent high pressure cooker test time/H₂O180 minutes/ 120 minutes/ 180 minutes/ pick-up/% pass 20s solder0.27%/100% pass 0.39%/100% pass 0.41%/0% pass T288 (minutes) 15 10 13 Cupeel (N/cm) 14.6 13.6 14.1 solder dip @ 288° C. (s) >180 103/106 4/5solder float @ 288° C. (s) >180 118/116 3/2 UL94 rating V-0 V-0 V-0 Dk @1 GHz, 25° C. 4.95 4.08 3.93 Df @ 1 GHz, 25° C. 0.018 0.020 0.021

The above results show that the use of modified D.E.R. 560, preparedaccording to Example 1, did not change the reactivity of the varnish andthermal stability remained similar. The modified brominated epoxy resinD.E.R. 560 still acted as an efficient fire retardant (UL94 V-0). Theincrease of modified D.E.R. 560 changed the appearance of the laminate,from clear yellow to white opaque, due to larger and more numerouspores. The dielectric constant of the nanoporous materials in Examples8A and 8B is much lower than the reference in Comparative Example III.

Bubbles in Example 8B are visible under the optical microscope. Thesebubbles are about 10-100 μm in diameter. Bubbles in the two othersamples were not visible under these conditions.

Transmission electron microscopy of Example 8A showed very small bubblesin the range of from 0.01 μm to 0.15 μm, with a number mean averagediameter of 0.059 μm. The reference Comparative Example III shows nobubbles under these conditions.

The diameter of pores in the laminate of Example 8A were as follows:

pores diameter 0.00- 0.02- 0.04- 0.06- 0.08- 0.10- 0.12- (μm) 0.02 0.040.06 0.08 0.10 0.012 0.14 >0.14 pores concen- 8.2 16.5 23.5 34.1 10.65.9 1.2 0 tration (%) Mean average diameters: Dn = 0.059 μm; Da = 0.065μm; Dv = 0.069 μm

EXAMPLE 9 AND COMPARATIVE EXAMPLE IV

In these Examples, modified D.E.R. 560, prepared according to Example2D, was used in a formulation of the present invention and compared toComparative Example IV without the modified D.E.R. 560, as described inthe following Table VI.

TABLE VI Comparative Example IV Example 9 FORMULATION (reference)(nanoporous) D.E.N. 438 [80% N.V. in MEK] (g) 189.69 189.69 modifiedD.E.R. 560 0.00 121.11 [70% N.V. in DOWANOL PMA] (g) D.E.R. 560 242.23121.11 [70% N.V. in DOWANOL PMA] (g) Perstorp 85.36,28 261.70 261.70[50% N.V. in DOWANOL PMA] (g) XZ 92505 90.43 90.43 [50% N.V. incyclohexanone] (g) boric acid solution 7.91 7.91 [20% N.V. in MeOH] (g)2E-4MI [20% N.V. in MeOH] (g) 5.200 5.200 PROPERTIES stroke curereactivity @ 170° C. (s) 234″ 233″ film Tg 163 168 (curing: 10′ @ 170°C. + 90′ @ 190° C.) (° C.) Hand Lay Up Prepreg Properties time in oven @180° C. (s) 180 180 residual get time (s) 65 65 pressing conditions8-ply, 8-ply, 90 minutes @ 190° C., 90 minutes @ 190° C. , 7 N/cm² 7N/cm² LAMINATE PROPERTIES appearance yellowish, homogeneous yellowish,homogeneous Tg (° C.) 152 152 T 288 (min) 18 15 CTE < Tg (ppm/K) 84 68CTE > Tg (ppm/K) 255 234 Cu peel (N/cm) not determined 14.6 Solder floatat 288° C. (s) 265 135 Solder dip at 288° C. (s) 250 130 UL 94 ratingV-0 (sum = 24 s) V-0 (sum = 24 s) Dk @ 1 MHz 25° C. 5.45 4.15 Df @ 1 MHz25° C. 0.013 0.012 Dk @ 10 MHz 25° C. 5.34 4.06 Df @ 10 MHz 25° C. 0.0130.012 Dk @ 100 MHz 25° C. 5.20 3.95 Df @ 100 MHz 25° C. 0.014 0.012 Dk @500 MHz 25° C. 5.08 3.87 Df @ 500 MHz 25° C. 0.016 0.013 Dk @ 1 GHz 25°C. 4.95 3.82 Df @ 1 GHz 25° C. 0.017 0.013

The above results show that the use of modified D.E.R. 560, preparedaccording to Example 2D, did not change the reactivity of the varnish;and Tg, thermal stability and flame retardancy remained similar. Thedielectric constant of the nanoporous material in Example 9 is muchlower than the reference in Comparative Example IV.

EXAMPLES 10A AND 10B AND COMPARATIVE EXAMPLE V

D.E.R. 560 was modified according to the procedure described in Example2D and used in the formulations described in Table VII below.

Thin (0.40 mm thick) laminates were pressed with and without applyingvacuum. Laminates pressed under vacuum and laminates pressed withoutvacuum showed similar thickness and resin content.

TABLE VII Comparative Example V Example 10A Example 10C FORMULATION (0%modified D.E.R. 560) (50% modified D.E.R. 560) (100% modified D.E.R.560) EPPN502H 197.418 197.418 197.418 [80% N.V. in MEK] (g) D.E.N. 438131.615 131.615 131.615 [80% N.V. in MEK] (g) D.E.R. 560 375.587 187.7930.000 [70% N.V. in DOWANOL PMA] (g) modified D.E.R. 560 0.000 187.793375.587 [70% N.V. in DOWANOL PMA] (g) Perstorp 85.36,28 450.073 450.073450.073 [50% N.V. in MEK] (g) XZ92505 107.311 107.311 107.311 [50% N.V.in cyclohexanone] (g) boric acid solution 13.146 13.146 13.146 [20% N.V.in MeOH] (g) 2E-4MI [20% N.V. in MEK] (g) 11.268 11.268 11.268PROPERTIES stroke cure reactivity @ 170° C. (s) 204 213 216 Hand Lay-UpPrepreg Properties time in oven @ 180° C. (s) 260 275 270 residual geltime (s) 44 49 50 Laminate with vacuum ON pressing conditions 2-ply,2-ply, 2-ply, 90 minutes @ 190° C., 90 minutes @ 190° C., 90 minutes @190° C., 50 N/cm² 50 N/cm² 50 N/cm² LAMINATE PROPERTIES appearance paleyellow, transparent pale yellow, transparent pale yellow, translucentlaminate resin content (%) 41 40 42 Tg (° C.) 185 185 185 relative Dk(arbitrary unit) reference = 1 0.98 0.92 Laminate with vacuum OFFpressing conditions 2-ply, 2-ply, 2-ply, 90 minutes @ 190° C., 90minutes @ 190° C., 90 minutes @ 190° C., 50 N/cm² 50 N/cm² 50 N/cm²LAMINATE PROPERTIES appearance pale yellow, transparent pale yellow,transparent pale yellow, translucent laminate resin content (%) 39 39 39Tg (° C.) 185 184 185 relative Dk (arbitrary unit) reference = 1 0.850.80

EXAMPLES 11A AND 11B AND COMPARATIVE EXAMPLE VI

D.E.R. 560 was modified according to the procedure described in Example3 and used in the formulations described in Table VIII below. Theresults of using varying amounts of the modified D.E.R. 560 aredescribed in the following Table VIII.

TABLE VIII Comparative Example 11A Comparative Example 11B ComparativeExample VI (50% modified D.E.R. 560 (50% modified D.E.R. 560 FORMULATION(0% modified D.E.R. 560) High Pressure) Low Pressure) SMA 3000 2380.82821.2 [50% N.V. in DOWANOL PMA/MEK] (g) D.E.R. 560 1799.0 [70% N.V. inDOWANOL PMA] (g) modified D.E.R. 560 2073.5 2073.5 [65% N.V. in DOWANOLPMA] (g) 2E-4MI 10.7 7.00 7.00 [20% N.V. in MEK] (g) PROPERTIES strokecure reactivity @ 170° C. (s) 210 258 258 pressing conditions 8-ply,8-ply, 8-ply, 90 minutes @ 190° C., 90 minutes @ 190° C., 90 minutes @190° C., no vacuum, 150 N/cm² no vacuum, 40 N/cm² no vacuum, 25 N/cm²LAMINATE PROPERTIES appearance whitish whitish whitish Tg (° C.) 178 180179 T 300 (min) 28 CTE < Tg (ppm/K) 73 CTE > Tg (ppm/K) 199 Cu peelN/cm) 9.0 9.0 UL 94 rating V-0 V-0 Dk @ 1 MHz 25° C. 4.29 4.10 4.01 Df @1 MHz 25° C. 0.009 0.008 0.007 Dk @ 100 MHz 25° C. 4.21 4.02 3.94 Df @100 MHz 25° C. 0.007 0.007 0.007 Dk @ 500 MHz 25° C. 4.18 3.99 3.89 Df @500 MHz 25° C. 0.010 0.008 0.008 Dk @ 1 GHz 25° C. 4.16 4.03 3.88 Df @ 1GHz 25° C. 0.012 0.007 0.007

EXAMPLES 12A AND 12B AND COMPARATIVE EXAMPLE VII

In these Examples, varying amounts of modified D.E.R. 539, preparedaccording to the procedure described in Example 4B, were used. As shownin Table IX below, the use of modified D.E.R. 539 did not change thereactivity of the varnish and Tg remained similar. The increase ofmodified D.E.R. 539 changed the appearance of the laminate, from clearyellow to white opaque, due to larger pores or due to a higher volumefraction of voids.

TABLE IX Comparative Example VII Example 12A Example 12B FORMULATION (0%modified D.E.R. 539) (50% modified D.E.R. 539) (100% modified D.E.R.539) D.E.R. 539-EK80 96.98 48.49 [80% N.V. in MEK] (g) modified D.E.R.539-EK80 50.44 100.87 [77% N.V. in MEK] (g) DICY solution 23.28 23.2723.27 [10% N.V. in DOWANOL PM/DMF] (g) 2-MI 0.427 0.465 0.504 [˜20% N.V.in MeOH] (g) DOWANOL PM (g) 2.39 0.41 0.00 PROPERTIES stroke curereactivity @ 170° C. (s) 229 232 231 film Tg 139 137 137 (curing: 10′ @170° C. + 90′ @ 190° C.) (° C.) Hand Lay-Up Prepreg Properties time inoven @ 180° C. (s) 250 250 250 residual get time (s) 82 84 89 prepregappearance shiny yellow pale yellow, slightly foamy pale yellow, foamypressing conditions 2-ply, 2-ply, 2-ply, 90 minutes @ 190° C., 90minutes @ 190° C., 90 minutes @ 190° C., 50 N/cm² 50 N/cm² 50 N/cm²LAMINATE PROPERTIES appearance yellow, transparent pale yellow,translucent very pale yellow, opaque

EXAMPLE 13

D.E.R. 560 was modified according to the procedure described in Example3, except with the composition described in the following Table X. Theresults of measurements carried out on the composition are alsodescribed in the following Table X.

TABLE X FORMULATION Example 13 anhydride hardener solution (AH1) 4137.2g [50% N.V. in DOWANOL PMA/MEK] E.R.L. 4299 232.8 g modified D.E.R. 560described in Example 3 2600.0 g [65% N.V. in DOWANOL PMA] boric acidsolution 38.6 g [20% N.V. in methanol] 2E-4MI 9.0 g [20% N.V. in MEK](g) PROPERTIES stroke cure reactivity @ 170° C. 272 s PREPREG PROPERTIESprepreg residual gel time 49 s prepreg minimum melt viscosity @ 140° C.170 Pa · s pressing conditions 30 minutes @ 190° C. + 60 minutes @ 210°C. 8-ply, no vacuum, 3.5 N/cm² LAMINATE PROPERTIES appearance whitish Tg(° C.) 183.5° C. T 300 (min) 20 minutes CTE < Tg 88 ppm/K CTE > Tg 240ppm/K Td onset 364° C. Cu peel 7.6 N/cm UL 94 rating V-0 Dk @ 1 MHz 25°C. 3.53 Df @ 1 MHz 25° C. 0.007 Dk @ 100 MHz 25° C. 3.45 Df @ 100 MHz25° C. 0.007 Dk @ 500 MHz 25° C. 3.41 Df @ 500 MHz 25° C. 0.007 Dk @ 1GHz 25° C. 3.40 Df @ 1 GHz 25° C. 0.007

EXAMPLE 14

A modified brominated epoxy resin solution was prepared in a 5 L glassreactor, equipped with a mechanical stirrer, and a heating jacket; andfitted with a N₂ inlet and an addition funnel. 1225.4 Grams of DOWANOLPMA, 2275.8 g of solid D.E.R. 560 and 310.3 g of E.R.L. 4299 werecharged into the reactor, and the solution was heated to 90° C. Aftercomplete dilution, the solution was cooled down to 25° C. 136.5 Grams ofdi-tert-butyl dicarbonate and 0.38 g of dimethyl aminopyridine wereadded to the solution in 4 portions over a period of 2 hours. Foamingoccurred after multiple charges of di-tert-butyl dicarbonate anddimethyl aminopyridine. After all of the di-tert-butyl dicarbonate anddimethyl aminopyridine was added, the solution was stirred for an extra2 hours at 25° C. No foaming was noticed after this period of time. Thesolution was transparent. Then, 51.7 g of boric acid solution (20%non-volatile in methanol) was added to the solution. The solution wasstirred for an extra hour. The theoretical epoxy equivalent weight forthe resultant resin was 401 (based on solids).

EXAMPLES 15A-15D

Modified bisphenol-A phenol novolac solutions were prepared in a glassreactor, equipped with a mechanical stirrer, and a heating jacket; andfitted with a N₂ inlet and an addition funnel. The percentage ofmodification of BPN 17 was 5.3%, 10%, 50% and 100% for Example 15A,Example 155B, Example 15C and Example 15D, respectively, as shown inTable XI below. The solutions of BPN17 were charged into the reactor anddi-tert-butyl dicarbonate and dimethyl aminopyridine were incorporatedinto the solutions in portions over a period of 2 h. Foaming occurredafter the charges of di-tert-butyl dicarbonate and dimethylaminopyridine were introduced into the reactor. After all of thedi-tert-butyl dicarbonate and dimethyl aminopyridine were incorporatedinto the reactor, the solution was stirred for an extra 2 hours. Nofoaming was noticed after this period of time. The solutions weretransparent.

TABLE XI FORMULATION Example 15A Example 15B Example 15C Example 15Dreaction temperature (° C.) 35 35 20-30 35 BPN17 [50% solids] (g) 3293.0592.6 459.8 320.2 DIBOC [80% solids in toluene] (g) 198.2 67.3 261.0363.5 DMAP (g) 0.44 0.15 1.17 0.81 PROPERTIES % modification of thephenolic groups 5.3 10 50 100 (calculated) (%)

EXAMPLES 16A-16D AND COMPARATIVE EXAMPLE VIII

In these Examples, various concentrations of thermolabile groups wereused to prepare the formulations as described in the following TableXII.

TABLE XII Comparative Example Example Example Example Example VIIIFORMULATION 16A 16B 16C 16D (reference) E-BPAPN solution [79.6% solids](g) 31.66 31.66 21.10 21.10 21.10 boric acid solution 1.23 1.23 0.820.82 0.82 [20% solids in methanol] (g) modified BPN17 as described inExample 15C 16.57 8.28 2.21 1.10 0 [58% solids] (g) BPN17 solution [50%solids] (g) 0 9.58 10.22 11.50 12.78 TBBA (g) 9.90 9.90 6.60 6.60 6.602-phenyl imidazole solution 0.38 0.38 0.25 0.25 0.25 [20% solids] (g)DOWANOL PM (g) 9.50 8.20 4.95 4.78 4.60 PROPERTIES stroke curereactivity @ 170° C. (s) 125 204 241 247 259 film appearance [cureschedule: 10 minutes @ opaque opalescent, clear, fine clear, clear, 170°C. + 90 minutes @ 190° C.] thick foam a lot of bubbles almost no nobubble bubbles bubbles

This Example illustrates that the final morphology of the epoxy matrixvaries with the concentration of thermolabile groups.

EXAMPLES 17A-17D AND COMPARATIVE EXAMPLE IX

In these Examples, various concentrations of thermolabile groups wereused to prepare the formulations as described in the following TableXIII.

TABLE XIII Comparative Example Example Example Example Example IXFORMULATION 17A 17B 17C 17D (reference) E-BPAPN solution [79.6% solids](g) 31.66 31.66 21.10 21.10 21.10 boric acid solution 1.23 1.23 0.820.82 0.82 [20% solids in methanol] (g) modified BPN17 as described inExample 15C 16.57 8.28 2.21 1.10 0 [58% solids] (g) BPN17 solution [50%solids] (g) 0 9.58 10.22 11.50 12.78 TBBA (g) 9.90 9.90 6.60 6.60 6.602-PhI solution [20% solids] (g) 0.60 0.60 0.60 0.60 0.60 DOWANOL PM (g)9.50 8.20 4.95 4.78 4.60 PROPERTIES film appearance [cure schedule: 30minutes @ opalescent clear, clear, clear, clear, 130° C. + 30 minutes @foam very fine no bubble no bubble no bubble 140° C. + 90 minutes @ 190°C.] bubbles

This Example illustrates that the final morphology of the epoxy matrixvaries with the concentration of thermolabile groups. A comparisonbetween Example 16 and Example 17 shows that the final morphology of theepoxy matrix varies with the processing conditions, such as the curingtemperature.

EXAMPLE 18 AND COMPARATIVE EXAMPLE X

In these Examples, formulations as described in the following Table XIVwere compared.

TABLE XIV Comparative Example X FORMULATION (reference) Example 18E-BPAPN solution [79.6% solids] (g) 248.0 248.0 modified BPN17 asdescribed 129.9 in Example 15B [58% solids] (g) BPN17 solution [50%solids] (g) 150.4 TBBA (g) 77.4 77.4 2-MI solution [20% solids] (g) 8.758.75 acetone (g) 30.2 50.7 PROPERTIES stroke cure gel time @ 130° C. (s)180 175 film appearance [cure schedule: clear, clear 15 minutes @ 130°C. + almost no very fine 60 minutes @ 190° C.] bubbles bubbles film Tg(mid point): 195.7/205.5 198.7/213.7 Tg1 (1^(st) scan)/Tg2 (2^(nd) scan)(° C.)

EXAMPLE 19

A modified brominated epoxy resin solution was prepared in a 5 L glassreactor, equipped with a mechanical stirrer, and a heating jacket; andfitted with a N₂ inlet and an addition funnel. 1131.9 Grains of DOWANOLPMA and 2102.1 g of solid D.E.R. 560 were charged into the reactor andthe solution was heated to 90° C. After complete dilution, the solutionwas cooled down to 35° C. 254.6 Grains of di-tert-butyl dicarbonatesolution (80% solids in toluene) and 11.4 g of dimethyl aminopyridinesolution (5% solids in MEK) were added to the solution drop-wise over aperiod of 30 minutes. After all of the di-tert-butyl dicarbonate anddimethyl aminopyridine were incorporated into the reactor, the solutionwas stirred for an extra hour at 35° C. No foaming was noticed afterthis period of time. The theoretical epoxy equivalent weight of theresultant product was 470 (based on solids).

EXAMPLES 20A-20E AND COMPARATIVE EXAMPLE XI

An epoxy resin solution was prepared by blending 608 g of D.E.R. 330,392 g of D.E.R. 6615 and 420 g of acetone (herein “Epoxy Blend”). 28.4Grams of the Epoxy Blend resin solution were weighed in glass bottles.Magnetic stirrers were placed in the bottles and the temperature wascontrolled at 22° C. Dicarbonate and dimethyl aminopyridine wereincorporated into the solution over a period of 30 minutes. The tablebelow describes the compositions used. The solutions were stirred for 24h at 22° C. After this period of time, solvent was removed in a vacuumoven at 22° C. for 24 h. Clear, very viscous liquids were finallyobtained.

The temperature at 1 wt % loss was measured by thermo-gravimetryanalysis (TGA). The results are shown in the following Table XV.

TABLE XV Comparative Example XI Example Example Example Example ExampleFORMULATION (reference) 20A 20B 20C 20D 20E Epoxy Blend solution [70.4%solids] (g) 28.4 28.4 28.4 28.4 28.4 28.4 DIBOC (g) 2.25 di-tert-amyldicarbonate (g) 2.23 diallyl pyrocarbonate (g) 2.31 diethylpyrocarbonate (g) 2.30 dimethyl pyroarcbonate (g) 2.35 DMAP [5% solidsin MEK] (g) 0.76 0.66 0.91 1.04 1.28 PROPERTIES % modification of thesecondary hydroxyl 0 50.8 44.6 61.1 69.9 86.4 groups (calculated) (%)weight % of grafted carbonate (calculated) 0 5 5 5 5 5 temperature at 1weight % loss 204 176 93 110 102 134 measured by TGA (° C.)

Example 20C gelled during heating to 190° C. This could be due toreactive multifunctional molecules coming from the decomposition productreleased during the cleavage of the thermolabile group.

EXAMPLES 21A AND 21B

In these Examples, the formulations, as described in the table below,were prepared; and the properties of the prepregs and laminates preparedtherefrom were measured. The results are shown in the following TableXVI.

TABLE XVI FORMULATION Example 21A Example 21B D.E.N. 438 solution [85%solids] (g) 34.16 1373.5 modified epoxy resin solution from 37.91 1566.7Example 19 (g) BPN17 solution [50% solids] (g) 48.06 XZ-92535 solution[50% solids] (g) 1644.5 boric acid solution [20% solids] (g) 1.39 52.22E-4MI solution [20% solids] (g) 0.60 24.62 MEK (g) 4.87 DOWANOL PMA25.9 PROPERTIES stroke cure gel time @ 130° C. (s) 365 265 film Tg (midpoint): 183.4/184.7 187.4/185.3 Tg1 (1^(st) scan)/Tg2 (2^(nd) scan) (°C.) PREPREG PROPERTIES prepreg residual get time @ 170° C. (s) 41prepreg minimum melt viscosity @ 41 140° C. (Pa · s) pressing conditions190° C. for 90 minutes (hot charge @ 180° C.), 2 kgf/cm² LAMINATEPROPERTIES appearance opalescent laminate Tg (mid point): 185/181 Tg1(1^(st) scan)/Tg2 (2^(nd) scan) (° C.) T 288 (min) 21 CTE < Tg (ppm/K)58 CTE > Tg (ppm/K) 179 high pressure cooker test 100% (120 minutes @120° C./ pass/water 20s solder dip @ 260° C.) pick-up = 0.34% UL 94rating V-0 (sum = 7s) Dk @ 1 MHz 25° C. 4.52 Df @ 1 MHz 25° C. 0.012 Dk@ 100 MHz 25° C. 4.36 Df @ 100 MHz 25° C. 0.012 Dk @ 1 GHz 25° C. 4.22Df @ 1 GHz 25° C. 0.012

EXAMPLES 22A-22D

In these Examples, the formulations, as described in the table below,were 110 prepared; and the properties of the prepregs and laminatesprepared therefrom were measured. The results are shown in the followingTable XVII.

TABLE XVII FORMULATION D.E.R. 560 solution [70% solids] 1420.7 g D.E.N.438 solution [85% solids] 1280.4 g modified BPN17 as described inExample 15A [50% solids] 1801.4 g boric acid solution [20% solids]  52.2g DOWANOL PMA  102.9 g 2E-4MI [20% N.V. in methanol]  29.83 g PROPERTIESstroke cure reactivity @ 170° C.   266 s film Tg (mid point): Tg1(1^(st) scan)/Tg2 (2^(nd) scan) 184.3/183.5° C. PREPREG PROPERTIESExample 22A Example 22B Example 22C Example 22D prepreg residual geltime @ 170° C. (s) 60 60 60 60 prepreg minimum melt viscosity @ 140° C.(Pa · s) 11.5 11.5 11.5 11.5 pressing conditions 190° C. for 190° C. for190° C. for 140° C. for 90 minutes, 90 minutes, 90 minutes, 10 minutes @0.5 kgf/cm² 1 kgf/cm² 2 kgf/cm² 0.5 kgf/cm² + 190° C. for 90 minutes @ 5kgf/cm² LAMINATE PROPERTIES appearance opalescent opalescent clearopaque thickness (cm) 1.55 1.66 1.49 1.44 laminate Tg (mid point):184/185 181/180 184/184 188/188 Tg1 (1^(st) scan)/Tg2 (2^(nd) scan) (°C.) T 300 (min) 9 6.2 10 7.3 CTE < Tg (ppm/K) 54 55 30 38 CTE > Tg(ppm/K) 229 226 224 217 Cu peel (N/cm) 12.7 UL 94 rating V-0 highpressure cooker test 100% 100% 100% 100% (60 minutes @ 120° C./pass/water pass/water pass/water pass/water 20s solder dip @ 260° C.)pick-up = 0.23% pick-up = 0.25% pick-up = 0.19% pick-up = 0.18% highpressure cooker test  50% 100% 100% (120 minutes @ 120° C./ pass/waterpass/water pass/water 20s solder dip @ 260° C.) pick-up = 0.56% pick-up= 0.57% pick-up = 0.50% Dk @ 1 MHz 25° C. 4.37 4.71 4.64 Df @ 1 MHz 25°C. 0.013 0.013 0.012 Dk @ 100 MHz 25° C. 4.19 4.62 4.43 Df @ 100 MHz 25°C. 0.014 0.014 0.014 Dk @ 1 GHz 25° C. 4.16 4.55 4.34 Df @ 1 GHz 25° C.0.015 0.015 0.013

EXAMPLE 23

A modified 2-ethyl-methyl imidazole solution was prepared in a glassbottle, equipped with a magnetic stirrer. 11.0 Grams of 2-ethyl-4-methylimidazole solution (20% solids in DOWANOL PMA) was weighed in the glassbottle; and 5.45 g of di-tert-butyl dicarbonate solution (80% solids intoluene) was incorporated into the solution drop wise over a period of 5minutes, at 20° C. Foaming happened during the incorporation ofdi-tert-butyl dicarbonate. After all of the di-tert-butyl dicarbonatehad been incorporated into the bottle, the solution was stirred for 48 hat 20° C. No foaming was noticed after this period of time. The solutionwas transparent.

EXAMPLES 24A-24F AND COMPARATIVE EXAMPLES XII-XIV

In these Examples, the formulations, as described in the table below,were prepared; and the properties measured are shown in Tables XVIII andXIX below.

TABLE XVIII Comparative Example Example Example Example FORMULATIONExample XII 24A 24B 24C 24D D.E.R. 592-A80 solution 60.44 60.00 60.0060.00 60.00 [80% solids] (g) DICY solution [10% solids] (g) 15.47 15.3615.36 15.36 15.36 2E-4MI solution [20% solids] (g) 0.484 modified 2E-4MIsolution from Example 23 [28% solids] (g) 0.34 0.65 1.31 1.63 DOWANOLPMA (g) 0.69 0.76 0.76 0.76 0.76 catalyst concentration (%, based onsolids) 0.19 0.19 0.37 0.74 0.92 2E-4MI concentration (%, based onsolids) 0.19 0.10 0.19 0.39 0.43 PROPERTIES stroke cure reactivity @170° C. 309 675 565 371 322

TABLE XIX Comparative Example Comparative Example FORMULATION ExampleXIII 24E Example XIV 24F D.E.R. 592-A80 solution 30.16 29.73 36.30 36.27[80% solids] (g) DICY solution [10% solids] (g) 7.72 7.61 9.29 9.292E-4MMI solution [20% solids] (g) 0.483 0.15 modified 2E-4MI solutionfrom Example 23 [28% solids] (g) 1.619 0.19 DOWANOL PMA (g) 0.70 0.101.14 1.18 catalyst concentration (%, based on solids) (%) 0.39 1.83 0.100.18 2E-4MI concentration (%, based on solids) (%) 0.39 0.96 0.10 0.10PROPERTIES stroke cure gel time @ 140° C. (s) 372 >900 stroke cure geltime @ 200° C. (s) 148 160

This Example shows that modified 2-ethyl-4-methyl imidazole solutionfrom Example 23 acts as a latent/blocked catalyst. At temperature lowerthan the unblocking temperature, the modified 2-ethyl-4-methyl imidazolesolution from Example 23, shows no catalytic activity or a much lowercatalytic activity than 2-ethyl-4-methyl imidazole. When the temperaturereaches the unblocking temperature, the catalytic activity of themodified 2-ethyl-4-methyl imidazole solution from Example 23 increases.Furthermore, the modified 2-ethyl-4-methyl imidazole solution fromExample 23 shows almost the same catalytic efficiency than2-ethyl-4-methyl imidazole at a temperature higher than the unblockingtemperature.

EXAMPLE 25

A modified phenol novolac solution was prepared in a glass bottle,equipped with a magnetic stirrer. 21.51 Grams of XZ-92535 phenol novolacresin solution (50% solids in DOWANOL PMA) were weighed in the glassbottle. The phenol novolac resin was modified with a stochiometricamount of di-tert-butyl dicarbonate in order to cap all phenol groups.28.15 Grams of di-tert-butyl dicarbonate solution (80% solids intoluene) and 0.38 g of dimethyl aminopyridine (solid) were incorporatedinto the solution in 5 portions over a period of 1 h, at 20° C. whilestirring. Foaming happened during the incorporation of di-tert-butyldicarbonate. After all di-tert-butyl dicarbonate has been incorporatedinto the bottle, the solution was stirred for 18h at 20° C. No foamingwas noticed after this period of time. The solution was transparent,with a low viscosity.

The Cannon-Fenske viscosity of XZ-92535 was 1166.1 cSt; and theCannon-Fenske viscosity of the modified XZ-92535 was 29.1 cSt.

This Example shows that capping the phenol groups of the phenol novolacresin with tert-butyl carbonate group drastically reduces the solutionviscosity, probably because of less hydrogen bonding effect.

EXAMPLE 26

A modified brominated epoxy resin solution was prepared in a glassbottle, equipped with a magnetic stirrer. 139.3 Grams of D.E.R. 560brominated epoxy resin solution (70% solids in DOWANOL PMA) was weighedin the glass bottle. 10.6 Grams of di-tert-butyl dicarbonate solution(80% solids in toluene) and 0.143 g of dimethyl aminopyridine (solid)were incorporated into the solution in portions over a period of 15minutes, at 25° C. under stirring. Foaming happened during theincorporation of di-tert-butyl dicarbonate. After all of thedi-tert-butyl dicarbonate was incorporated into the solution, thesolution was stirred for 48 h at 25° C. No foaming was noticed afterthis period of time. The solution was transparent, with a low viscosity.

The Cannon-Fenske viscosity of D.E.R. 560 brominated epoxy resinsolution was 262.3 cSt; and the Cannon-Fenske viscosity of the modifiedD.E.R. 560 brominated epoxy resin solution was 198.0 cSt.

This Example shows that capping the secondary hydroxyl groups of thebrominated epoxy resin solution with tert-butyl carbonate groups reducesthe solution viscosity, probably because of less hydrogen bondingeffect.

EXAMPLE 27

To perform the modification in this Example, a 12 L round bottomed flaskwith a 5-neck fitted lid and equipped with a condenser, mechanicalstirrer, N₂ inlet, addition funnel and thermocouple was used. An 80%solids solution of D.E.R. 592 (10 kg, dark brown solution) was chargedinto the flask followed by the addition of acetone (589 g) to. reducethe solution viscosity. Di-tert-butyl dicarbonate (168.7 g, colorlessliquid) was then added to the reactor and the solution was heated to 40°C. Dimethyl aminopyridine (0.48 g, white crystalline solid) wasdissolved in acetone and added drop-wise to the solution. The additionproceeded over a 30 minute time period to reduce the amount of foamingin the reactor. After the addition was complete, the solution wasstirred for an additional 3 hours. At the beginning of this time period,the solution was dark brown in color and filled with bubbles. Atcompletion, no bubbles remained.

EXAMPLES 28A-28D

In these Examples, the formulations, as described in the table below,were prepared; and the properties measured are shown in Tables XX andXXI below.

TABLE XX FORMULATION modified D.E.R. 592 solution as described inExample 27 [76% solids]   7055 g XZ 92505 solution [50% solids]   643 gboric acid solution [20% solids]  161.7 g acetone    80 g 2E-4MI [10%solids] 1341.6 g PROPERTIES stroke cure reactivity @ 150° C.   265 sprepreg residual gel time @ 170° C.    81 s

TABLE XXI Example 28A Example 28B Example 28C Example 28D pressingconditions 190° C. for 150° C. for 150° C. for 150° C. for 90 minutes,15 minutes + 15 minutes + 15 minutes + 100 psi 190° C. for 190° C. for190° C. for 90 minutes, 90 minutes, 90 minutes, 60 psi 45 psi 30 psiLAMINATE PROPERTIES appearance brown and clear brown and cloudy brownand cloudy brown and cloudy laminate Tg (mid point): 167/172 174/180174/179 Tg1 (1^(st) scan)/Tg2 (2^(nd) scan) (° C.) T 260 (min) 7 7 7 Td,5% wt loss (° C.) 302 302 301 CTE < Tg (ppm/° C.) 26 42 65 CTE > Tg(ppm/° C.) 307 328 332 Cu peel (lb/in.) 4.4 4 3.91 3.85 UL 94 rating V-0V-0 V-0 Dk @ 1 MHz 25° C. 4.56 4.14 4.05 4.03 Df @ 1 MHz 25° C. 0.010.01 0.01 0.01 Dk @ 100 MHz 25° C. 4.38 3.97 3.88 3.86 Df @ 100 MHz 25°C. 0.01 0.01 0.01 0.01 Dk @ 1 GHz 25° C. 4.47 3.86 3.74 3.75 Df @ 1 GHz25° C. 0.02 0.01 0.01 0.01

EXAMPLES 29A-29E

In these Examples, the formulations, as described in the table below,were prepared; and the properties measured are shown in Table XXIIbelow.

TABLE XXII FORMULATION modified D.E.R. 592 solution as described inExample 27 [76% solids]   7455 g DICY [10% solids 1643.5 g 2-MI [10%solids]  198.9 g PROPERTIES stroke cure reactivity @ 150° C.   297 sprepreg residual gel time @ 170° C.    81 s Example 29A Example 29BExample 29C Example 29D Example 29E pressing conditions 175° C. for 175°C. for 130° C. for 175° C. for 130° C. for 60 minutes, 60 minutes, 15minutes + 60 minutes, 15 minutes + 100 psi 60 psi 175° C. for 45 psi175° C. for 60 minutes, 60 minutes, 60 psi 30 psi LAMINATE PROPERTIESappearance yellow and clear yellow and clear yellow and clear yellow andclear yellow and clear laminate Tg (mid point): 154/155 156/155 152/155159/159 Tg1 (1^(st) scan)/Tg2 (2^(nd) scan) (° C.) T 260 (minutes) 7 7 46 Td, 5% wt loss (° C.) 301 302 302 301 CTE < Tg (ppm/° C.) 114 65 84CTE > Tg (ppm/° C.) 208 242 233 375 Cu peel (lb/inch) 6.3 5.92 5.97 6.36UL 94 rating V-0 V-0 V-0 V-0 Dk @ 1 MHz 25° C. 4.5 4.34 4.49 4.28 4.1 Df@ 1 MHz 25° C. 0.01 0.01 0.01 0.01 Dk @ 100 MHz 25° C. 4.36 4.14 4.294.08 3.96 Df @ 100 MHz 25° C. 0.01 0.01 0.01 0.01 Dk @ 1 GHz 25° C. 4.364.09 4.12 3.92 3.79 Df @ 1 GHz 25° C. 0.01 0.01 0.01 0.01

EXAMPLE 30

A modified high molecular weight epoxy resin solution was prepared in a1 L glass reactor, equipped with a mechanical stirrer, and a heatingjacket; and fitted with a N₂ inlet and an addition funnel. 316.6 Gramsof D.E.R. 669E solution [40% NV in DOWANOL PMA] were charged into thereactor and the temperature was controlled between 25° C. and 30° C.118.8 Grams of di-tert-butyl dicarbonate solution [80% NV in toluene]and 5.32 g of dimethyl aminopyridine solution [10% N.V. in MEK] wereadded dropwise to the solution over a period of 2 hours. Foamingoccurred during the incorporation of di-tert-butyl dicarbonate anddimethyl aminopyridine. After all of the di-tert-butyl dicarbonate anddimethyl aminopyridine were incorporated into the solution, the solutionwas stirred for an extra 2 hours at 25° C. The solution was transparent.The theoretical epoxy equivalent weight was 4179 (based on solids).

The modified D.E.R. 669E solution was then used as an epoxy-functionalfoaming agent additive in electrical laminates formulations.

The Cannon-Fenske viscosity at 25° C. of D.E.R. 669E solution [40% N.V.]was 1542 cSt; and the Cannon-Fenske viscosity at 25° C. of the modifiedD.E.R. 669E solution [40.4% N.V.] was 743 cSt.

EXAMPLE 31

In this Example, the formulation, as described in the table below, wasprepared and the properties measured are shown in Table XXIII below.

TABLE XXIII FORMULATION XZ-92567.01 [65% NV] 1994.2 g XZ-92568.01 [50%NV] 2351.4 g modified epoxy resin described in Example 30  254.1 g [40%NV] DOWANOL PMA  122.4 g 2E-4MI [20% N.V. in DOWANOL PMA]  5.20 gPREPREG PROPERTIES prepreg residual gel time @ 170° C.    72 s prepregminimum melt viscosity @ 140° C.   410 Pa · s pressing conditions 190°C. for 90 minutes, 10 kgf/cm² LAMINATE PROPERTIES appearance opaque,homogeneous laminate Tg measured by DMTA @ 10 Hz 194° C. high pressurecooker test 100% pass/ (120 minutes @ 120° C./ waterpick-up = 0.30% 20ssolder dip @ 260° C.)

1. A process for making a nanoporous substrate comprising the steps of:(a) grafting onto a backbone of an organic resin, a thermolabilefunctionality by reacting hydrogen active groups of the organic resinwith a compound containing thermolabile group; (b) preparing acomposition by blending the organic resin containing thermolabile groupswith at least a curing agent; and (c) thermally degrading thethermolabile groups grafted on the organic resin such as to produce ananoporous substrate.
 2. The process of claim 1 wherein the substrate isa laminate.
 3. The process of claim 1 wherein the organic resin isselected from the group consisting of epoxy resins, phenolic resins,polyimide resins, polyamide resins, polyester resins, polyether resins,bismaleimide triazine resins, cyanate ester resins, vinyl ester resins,hydrocarbon resins, and mixture of thereof.
 4. The process of claim 1wherein the organic resin is an epoxy resin.
 5. The process of claim 1wherein the organic resin is a brominated epoxy resin.
 6. The process ofclaim 1 wherein the organic resin is a phosphorus-containing epoxyresin.
 7. The process of claim 1 wherein the organic resin is an epoxyresin with an epoxy equivalent weight higher than
 500. 8. The process ofclaim 1 wherein the hydrogen active group is selected from the groupconsisting of amines, phenols, thiols, hydroxyls, alcohols, amides,lactams, carbamates, pyrroles, mercaptans, imidazoles, guanidine andmixtures thereof.
 9. The process of claim 1 wherein the compoundcontaining the thermolabile group is selected from the group consistingof dicarbonates, derivatives of dicarbonates, carbazates, derivatives ofcarbazates, and mixtures thereof.
 10. The process of claim 1 wherein thecompound containing the thermolabile group is tert-butyl dicarbonate.11. The process of claim 1 wherein the thermolabile group is acarbonate.
 12. The process of claim 1 wherein the thermolabile group istert-butyl carbonate.
 13. The process of claim 1 wherein thethermolabile group is present in the composition in an amount such thatthe weight percent of thermolabile groups in the composition is betweenabout 0.01 weight percent and about 10 weight percent, based on solids.14. The process of claim 1 including a solvent.
 15. The process of claim14 wherein the solvent is a ketone, an acetate of glycol ethers ormixtures thereof.
 16. The process of claim 14 wherein the solvent ispresent in an amount of from about 10 parts to about 60 parts.
 17. Theprocess of claim 1 including a catalyst for the reaction between theorganic resin and the compound containing the thermolabile group. 18.The process of claim 17 wherein the catalyst is dimethyl aminopyridyne.19. The process of claim 1 wherein the reaction between the organicresin and the compound containing the thermolabile group is done at atemperature of from about 15° C. to about 45° C.
 20. The process ofclaim 1 including adding a thermoplastic compound to the composition tolower the dielectric constants.
 21. The process of claim 20 wherein thethermoplastic compound is polyphenylene ether, polyphenylene oxide, orallylated polyphenylene ether.